The invention relates to a mechanism for monitoring the operating efficiency of an exhaust recalculation valve for an internal combustion engine, with a pressure sensor that determines the pressure in a suction valve of the internal combustion engine.
The pollutant emission of internal combustion engines can be improved by a process termed exhaust recalculation. For this purpose there is provided on the exhaust side of the internal combustion engine an exhaust recalculation valve which controls an exhaust recalculation line ending on the intake side of the internal combustion engine in the intake pipe downstream from the throttle valve. Exhaust is added to the air intake and as a result chiefly the No. Exhaust of the internal combustion engine is reduced.
Since the exhaust recalculation valve represents an exhaust relevant component, its operating efficiency in motor vehicles must be monitored partly on the basis of already existing legal regulations (ODD II). Malfunctions which occur must be stored in a malfunction storage unit for the purpose of display in customer service inspections. The pressure in the intake pipe downstream from the throttle valve increases as a result of opening of the exhaust recalculation valve, that is, addition of exhaust to the air intake.
A simple method of monitoring the exhaust recalculation valve consists of mounting a suitable pressure sensor directly in the suction pipe or at the end of a negative pressure line (U.S. Pat. No. 5,337,725) branching off from the suction pipe, in order to register change in pressure when the exhaust recalculation valve is actuated. Mounting of a pressure sensor such as this on the intake pipe however is very costly from the viewpoint of installation and/or is not always possible because of considerations of space.
Another possibility for monitoring the exhaust recalculation valve is that of mounting the pressure sensor in a connecting line branching from the intake pipe, a line which leads to a compressed-air actuating element such as a vacuum-operated servo brake or vacuum dashpot switching intake pipe. However, this arrangement entails the disadvantage that uncontrollable pressure changes occur in the connecting line involved when such an operating element is actuated. If however an accidental simultaneous actuation of an operating element such as this occurs during testing of operation of the exhaust recalculation valve, the pressure sensor mounted in this connecting line erroneously registers changes in pressure which are not to be attributed to operation of the exhaust recalculation valve. On occasion this can result in generation of an erroneous operational verification result.
It is claimed for the invention that a mechanism with pressure sensor is provided for an internal combustion engine, a sensor in which the disadvantages indicated are avoided, assembly of which is simple and cost-effective, and which simultaneously permits reliable operational testing.
This result is obtained by means of the mechanism with the features described in the patent claim. The essential concept of the invention is represented by mounting the pressure sensor in a line leading to a fuel pressure regulator. A fuel pressure regulator such as this is not in the form of a pneumatic consuming device, that is, no sudden accidental pressure changes which would result in falsification of the measured value in operational testing can occur in the connecting line leading to this fuel pressure regulator. Hence reliable operational testing of the exhaust recalculation valve is made possible by this mounting of the pressure sensor.